The present invention relates to a method and an apparatus for obtaining a magnification error in a first direction, and particularly to a method and an apparatus for obtaining a magnification error in the longitudinal direction for an image scanning apparatus.
In recent years, an image scanner has become an indispensable peripheral equipment of personal computers. Many manufacturers are trying their best to improve the scanning quality.
In a scanner, the driving device for driving the image-picking device has a mechanical error in the moving direction of the image-picking device (or the longitudinal direction). For a scanner with a resolution of 600 dots per inch (DPI), the image-picking device driven by the driving device will move 6000 steps for scanning a document with a length of 10 inches to obtain an image having 6000 dots in length. However, due to above-described error, the image-picking device must move 6060 steps to finish the scanning process so that the actual length of the scanned image is up to 6060 dots, resulting in that the length of the scanned image changes from 10 inches to 10.1 inches.
Therefore, it is desirable to provide a method and an apparatus for obtaining a magnification error in the longitudinal directions to improve the scanning quality.
An object of the present invention is to provide a method for obtaining a magnification error in a first direction for an image scanning apparatus. The method includes steps of (a) providing a marking pattern having a particular length in the first direction, (b) scanning the marking pattern to obtain a scanning length in the first direction, and (c) calculating the magnification error in the first direction from the scanning length and the particular length.
According to the present invention, the marking pattern is mounted on one side of an object to be scanned and the marking pattern further includes a rectangular pattern with a first color and a background with a second color. Preferably, the first color and the second color are black and white respectively. The marking pattern further includes a plurality of spaced rectangular patterns and a background. Besides, the step (b) is executed by an image-picking device. The marking pattern intersects with a moving path of the image-picking device. In addition, the first direction is a moving direction of the image-picking device driven by a driving device, that is, a longitudinal direction. The driving device is connected with the image-picking device for driving the image-picking device to scan in the first direction.
Another object of the present invention is to provide an image scanning apparatus obtaining a magnification error in a first direction. The image scanning apparatus includes an image-picking device for picking digital data representative of an image, a driving device connected to the image-picking device for driving the image-picking device to scan in the first direction, a scanning platform for placing thereon an object to be scanned, and a marking pattern having a particular length in the first direction on the scanning platform.
In accordance with the present invention, the image scanning apparatus is one selected from a group consisting of an image scanner, a photocopier, and a fax machine. The image-picking device is preferably a charge coupled device (CCD). In addition, the first direction is a moving direction or a longitudinal direction of the image-picking device driven by the driving device.
The present invention may best be understood through the following description with reference to the accompanying drawings, in which: